A guide wire is used for guiding a catheter to a treatment site where it is difficult to perform a surgical operation. For example, a guide wire may be used in percutaneous transluminal coronary angioplasty (PTCA) or treatment which is aimed to be less invasive to the human body, or used in tests such as cardioangiography. The guide wire used in PTCA is inserted into the vicinity of a stenosed site of a blood vessel (i.e., the target site) together with a balloon catheter in a state in which a distal end of the guide wire protrudes from a distal end of the balloon catheter. The distal portion of the balloon catheter is thus guided by the guide wire to the vicinity of the stenosed site of a blood vessel.
Blood vessels are complicatedly curved. Therefore, a guide wire used when inserting a balloon catheter into a blood vessel requires suitable flexibility and resilience with respect to bending, pushability and torquability (which are collectively called “operability”) for transmitting an operation at a proximal portion to a distal side of the guide wire. A guide wire also requires suitable tensile strength, kink resistance (bending resistance), and the like. A configuration for obtaining suitable flexibility and resilience includes a structure of a double metal coil (being flexible with respect to bending) around a thin distal core of a guide wire and a structure in which a super elastic wire such as Ni—Ti wire is used in a core of a guide wire. An example is disclosed in U.S. Pat. No. 7,785,274. In addition, a reinforcing material that is separately provided at a distal portion of a core is known to improve torquability (i.e., ability to transmit torque to a distal portion of the guide wire so that the guide wire can be maneuvered such as being rotated and/or twisted).
When the guide wire is used for PTCA, pushability is decreased if the distal portion of the core is thin, so that the guide wire may be used as safely as possible while avoiding penetration of a wall of a blood vessel. However, a transverse cross-sectional area should not be excessively reduced in order to maintain sufficient tensile strength of the guide wire so as to avoid breakage. Furthermore, in some cases, reshaping of the distal portion of the core is performed during PTCA. For example, the distal portion of the core may be pressed into a flat plate shape in order to easily perform this reshaping. Accordingly, the pushability of the distal end decreases, thereby improving safety. However, torquability significantly decreases. In addition, although the torquability may be improved when the reinforcing material is separately provided, it is difficult to perform the reshaping of the distal portion of the core.
Therefore, in the guide wire in the related art, it is difficult to achieve coexistence of improvement in easiness of the reshaping at the distal portion and torquability up to the distal portion while maintaining safe pushability and tensile strength.